alt Hacker NewsWait, capped at 24 kWh a day? Our household consumed 8 kWh per day over the past week (gas cooking, no airco). So with a home battery that sinks 10 kWh during those 3 hours you have minimal energy costs?
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Forget 3hrs free. We lived in the tropics in Australia with a ~6kW system and often had negative quarterly invoices (i.e. got paid by our retailer) ... esp. in winter months. Aircon, pool, appliances all electric. At the very least the pool pump ran free all year round.
Edit: should add, that's straight solar no battery
Yes - the regulated offer is capped at 24 kWh per day but some retailers such as Globird and CovaU are offering plans which include up to 50 kWh per day of ‘free’ electricity. With a large enough battery and inverter you could just end up paying daily supply charges of $1.65-2.20 per day.
Just for reference our fully electric household (including cooking, water and aircon). Highest usage this month on a very hot day was 25kWh. (Disclaimer: I am not in Australia. Already cover most of it with roof solar. No battery yet)
I pay about 38c per kilowatt plus $1.70 per day for the connection fee. So by that maths, you'd save 8×0.38=$3.04 per day. A 10kWh battery is in the ballpark of $4000. So it'll take about 4 years to break even. Then you'd just have to pay the connection fee, which seem to be increasing every year.
This is what I am doing. 42 kWh battery, 6 kW solar and fully electrified house, 2x EVs. I am able to charge cars at work and so in the depths of winter I am able to run the house by charging during the 3 hour window. There have been just a couple of cold (~2-4 degC) days when the battery was depleted 1-2 hours before the window starts.
As the weather warms and we get more solar exposure we will easily be in excess. We get a very small export rate with a bonus for no energy consumption during peak evening hours which can offset the fixed daily charge.
There are a lot of gotchas that you need to be aware of. 42 kWh is nominal capacity not the actual usable capacity. House load, max grid import and export capacity, max inverter capacity, AC or DC coupled panels, battery charging profile, battery temp are all factors in how much you can charge in the window. For example I have max 15 kW grid draw, with a 10 kW inverter that can charge the battery. I can put in max ~30 kWh into the battery, so I also run other loads in the house to use the other 5 kW capacity. If I go over 5 kW house load the battery charge is clipped to maintain grid import limit.